Portable power supply



FIG. 1 is a perspective view of a portable power supply showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines in the drawings are included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

CLAIM The ornamental design for a portable power supply, as shown and described. 